Anodic
aluminum oxide (AAO) membranes with aligned, cylindrical, nonintersecting pores were selectively functionalized in order to create dual-functionality substrates with different pore-rim and pore-interior surface functionalities, using
silane chemistry. We used a two-step process involving an evaporated thin
gold film to protect the underlying surface functionality of the pore rims. Subsequent treatment with
oxygen plasma of the modified AAO membrane removed the unprotected organic functional groups, i.e., the pore-interior surface. After
gold removal, the substrate became optically transparent, and displayed two distinct surface functionalities, one at the pore-rim surface and another at the pore-interior surface. We achieved a selective hydrophobic functionalization with dodecyl-
trichlorosilane of either the pore rims or the pore interiors. The deposition of planar
lipid membranes on the functionalized areas by addition of small
unilamellar vesicles occurred in a predetermined fashion. Small
unilamellar vesicles only ruptured upon contact with the hydrophobic substrate regions forming solid supported hybrid bilayers. In addition, pore-rim functionalization with dodecyl-
trichlorosilane allowed the formation of pore-spanning hybrid
lipid membranes as a result of giant unilamellar vesicle
rupture. Confocal
laser scanning microscopy was employed to identify the selective spatial localization of the adsorbed fluorescently labeled
lipids. The corresponding increase in the AAO refractive index due to
lipid adsorption on the hydrophobic regions was monitored by optical waveguide spectroscopy. This simple orthogonal functionalization route is a promising method to control the three-dimensional surface functionality of nanoporous films.